AM 580 has been around at least as long as CKLW, as least in my lifetime. As a kid growing up right across the river from the CKLW TV tower, CKWW played "Middle of the Road" music (pop songs for the older folks) with local personalities. They said "Wonderful Windsor" a lot. It was always the local Windsor station, not trying to serve Detroit listeners much, until their ownership also got permission to operate CKLW and Windsor became a "one-owner" commercial radio market. That's when they moved the all-talk format CKWW had by then to the big signal on AM 800. Not a smart move, in my opinion, since CKLW barely shows up anymore in any ratings in Detroit, Toledo, or Cleveland, where it still comes in like a local signal and used to have a significant audience, whereas the 500 watts on am580 covers Essex County nicely and much of Detroit.
After they swapped the adult standards format that CKLW had gone to onto CKWW 580, there was a short time (a couple of years, perhaps), where AM580 operated with higher power and put a solid signal south into Toledo. Local press was that the signal on 580 was upgraded to accommodate the disappointed listeners who missed the standards on CKLW. But it went back to the weaker 500watts and is still audible in Ohio now, but weaker, with a lot of hiss and fade outs.
Since there are few oldies or standards stations in most of the other markets where CKLW's daytime signal reaches (I think Sandusky's AM1450 WLEC is the one exception), they could probably make money and some inroads outside of Windsor if they swapped the programming on 580 and 800 back again.
Then again, I still think the CBC should have use of the 50kw of CKLW, as a way to remedy the mistake of shutting down the 50kw CBC stations in Toronto and Montreal some years ago for "FM only," and as a way to provide CBC Radio One programming to at least a few listeners inside the US in Michigan, Ohio, and a bit of Indiana and Pennsylvania.
Much of the programming on 800 now is the same syndicated American talk shows you hear on other US stations. And their popular morning drive show is all about Windsor, so why not put it on a local frequency and put something more specialized on the big 8, where a specialty format can reach a large enough audience to pay for itself? They're not making any real money off of it anymore outside Canada with the current talk format on CKLW. Not sure the owners even care anymore.
The Canadian regulators at the CRTC do assign frequencies based on content and require targeted audiences to be served by specific stations. It seems consistent with their policies to make better use of the AM facility assignments in Windsor to promote Canadian interests and information reaching outside their borders to the non-insignificant population that AM 800 can reach.